Apparatus for casting dental restorations



June 21, 1949.

l. HORDES APPARATUS FOR CASTING DENTAL RESYORATIONS Filed April 19, 1947 INVENTOR. IRVING HORDES ATRNEY Patented June 21, 1949 UN [TED OFFICE- APPARATUS FOR CASTING DENTAL RESTORATIONS Irving Hordes, Yonkers, N. Y.

Application April 19, 1947, Serial No. 742,696

6 Claims. 1

This invention relates particularly to improvements in apparatus for use in the casting of dental restorations, that is, in forming a bridge, an artificial tooth or part thereof, such as, an inlay, crown and the like and other dental structures, and this application is a continuation in part of my copending' application Serial Number 639,078 filed January 4, 1946 which has become Patent 2,424,698.

A primary object of the present invention is to produce a novel apparatus which is particuiarly suited for casting dental restorations using a plastic or other suitable material as the casting material.

Another object is to provide means for keeping the plastic clean.

Another object is to provide means for preventing particles of investment material entering into the mold.

Another object is to eliminate the necessity for a protective coating on the sprue.

Another object is to provide a mold within a flask in Which hand packing and automatic pressure combined or automatic pressure alone may be used to condense the plastic material and augment the supply thereof to the cavity in which the restoration is to be formed, thus assuring a thoroughly condensed plastic composition.

Another object is to provide apparatus of this kind that is easily manipulated, is inexpensive, comparatively simple in construction and readily adjustable to meet any requirements in the casting of dental restorations.

Other objects and advantages of the invention will be apparent from the description thereof to follow taken in connection with the accompanying drawing in which:

Fig. 1 is a vertical sectional view of my improved apparatus showing the flask in position on its support and with the spine forming members in position and carrying a wax pattern which forms the mold in the investment material.

Fig. 2 is a vertical sectional view of the improved apparatus in position on a clamping device and showing the position of the parts for receiving plastic material in the mold in the flask.

Fig. 3 is a top plan view of the apparatus as shown in Fig. 1.

Fig. 4 is a side elevation-a1 view on a large scale of the sprue forming members and pattern.

Fig. 5 is a bottom plan view of the parts shown in Fig. 4.

Fig. 6 is an enlarged sectional view of the outer sprue member.

Fig. '7 is a part sectional and part elevational view of the inner sprue member.

The plastic material used for making dental restorations should be in a soft but viscous state, that is, about the consistency of putty or a thick paste. Plastic in this condition may be obtained or prepared in two ways. Powdered or granulated plastic in its cured or polymeric form is mixed with a portion of the plastic in liquid or monomeric form in a manner known to the dental technician in preparing plastic to be used for forming dental acrylic jacket crowns, inlays and the like. The viscous plastic may be obtained also by using polymeric plastic in powdered, granular or biscuit form and heating it until it has the proper viscous consistency.

The investment material for the casting may be formed in the customary manner using known materials such as plaster of Paris or the like.

Referring to the drawing, a wax pattern I0 is formed in a known manner after which it is mounted upon a pin I l. A cavity forming metal sleeve or outer sprue member 1'2 is formed with an inwardly tapered shoulder l3 at one end pro-- viding a restricted opening at said end and with a flange or base M at its other end. A disc-like base or support I5 has a central internally screwthreaded opening I6 and is provided with a counter-sunk recess I1 around said opening IS. The flange I4 of the sprue member I2 is formed with an external screw thread which is adapted to engage an internal screw thread on the wall of the recess I! to seat the sprue member on the base l5 so that the upper surface of the flange I4 is level with the upper surface of the disclike base I5 as seen in Fig. 1.

Another sprue member I8 is positioned inside of the sprue member l2 and is formed with a tapered body portion I9 having a base or flange 2.9 at one end and a neck portion 21 at its other end. The body portion is formed with spaced slits 22 extending through the neck portion. The base 20 is provided with external screw threads as indicated at 23. A passage 24 extends centrally through the body portion. To position the inner sprue member l8, it is inserted through the central opening IS in the disc-like member I5 and through the outer sprue member l2 so that its neck portion 2! protrudes through the opening in said sprue member I2. The threads on the base 2 0 are brought into engagement with the threads in the opening It in the base I5. The pin II with its wax pattern I 0 is loosely dropped into the passage 24 of the sprue member It. The screw threaded base is set upon by a suitable tool whereby its slitted neck portion it! engages the wall of the restricted opening in the outer sprue member I2 and becomes compressed and grips the pin II thereby serving as a chuck member to hold the pin with its wax pattern spaced away from the outer sprue member !2.

A sectional flask is removably supported on the disc-like base I5 around the sprue members. This flask comprises a lower mold section 26 and an upper mold section 21 as shown in Fig. 1, said sections having interlocking flange portions on their edges and may have pry-notches on said edges to facilitate separation of the sections. The mold sections have tapered inner walls in opposed relation.

In using the improved apparatus, investment material 28 is poured into the lower section 26 to or approximately to the upper edge thereof and tapped leaving a portion of the wax pattern projecting above said investment material. The investment material is then permitted to harden. A coating of separating material may then be applied to the upper surface of the investment material in said section 26 to facilitate separation of the flask sections. The upper section 2'! is then filled with investment material in the same manner. The investment material is then permitted to harden. The base I5 and flask 25 are then placed in boiling water and the wax melted out. The two sections 26 and 2'! are separated and the pin II and inner sprue member I8 removed leaving the sprue sleeve I2 embedded in the investment material and leaving a cavity or mold 29 in the material where the wax pattern m was and leaving a chamber 30 inside the sprue I2 where the inner sprue I8 was, said chamber and mold 29 being connected by a passage or gate 3| as shown in Fig. 2. The disc-like member I5 had been unscrewed from the sprue member I2 after the inner sprue I8 and pin I I were removed. Opposed notches 32 in the outer surface of the wall of the sprue member I2 which interlock with the material in the section 26 prevent said sprue member l2 from turning when the disc-like member I5 is being removed. These notches also provide means for receiving a tool when screwing the sprue member I2 to the disc-like member I5, and also prevent lengthwise movement of the sprue member I2 in the investment material.

The apparatus is thus prepared to receive the plastic material.

The flask with its contents is next placed on a clamping apparatus consisting of a frame 33 preferably formed of a casting having a rectangular base 34 with an upwardly extending post 35 at each corner. Between the posts 35 on each side is another guide post 36 having a screw threaded upper end, which posts project above the posts 35. The upper surface of the base 34 is formed with a countersunk recess portion 31 at its center. Slidably and detachably mounted on the posts 36 is a plate 38 having end openings for receiving the posts 36 and having a central opening 38.

The sections of the flask are mounted on the base 34 under the plate 38 in superimposed or inverted relation, that is, section 21 is seated on the base 34 in the central recess portion 31. section 26 with the sprue member I2 embedded therein is on top of the section 21, the flange I4 of the sprue member I2 projecting slightly above the top of the investment material in section 26 as shown in Fig. 2. When the flask sections are thus potil) 4 sitioned, the plate 38 rests on the upper edge of the flask section 26 and the flange I 4 of sprue member I 2 fits in the central opening 39 and seals this opening. Nuts 46 on the posts 36 above the plate 38 clamp the flask sections together and hold them against displacement on the base 34.

Plastic material AI is then forced into the cavity or mold 29 through the chamber 36. This material is first tightly packed by hand and then pressure is exerted thereon by suitable pressure apparatus in the usual manner, only the plunger 42 of such apparatus being shown. When suiflcient pressure has been exerted and the material has been properly packed in the mold, the entire apparatus is placed in a hot bath, oven, furnace or the like until the plastic material hardens or sets. After processing the casting it is allowed to cool and the sections of the flask are then separated by a suitable tool. The restoration is then removed from the investment material and cleaned.

The sprue member I2 is an important feature of the present invention as in addition to forming a sprue in the investment material, it also provides means for supporting the pattern in proper position within the soft investment material until it hardens. The flange portion Id of the member I2 affords additional resistance to the downward pressure of the plunger against the body of the said member I2 and said flange portion It with the plate 38 seals the investment material in the flask during the processing. This member I2 also keeps the plastic material clean as the plunger will press against the inner wall thereof and will not force particles of investment material into the mold. It also eliminates the necessity of a protective coating as the case where the chamber is made of investment material, and furthermore it is so shaped that it facilitates the removal of the surplus plastic material. The notches 32 in the wall of the sprue member 52 permit said member to be unscrewed or tightened on the disc member I5. Such notches also prevent rotation and longitudinal movement of the sprue member in the investment material.

The plunger 42 may be provided with a guide line 43 on its surface for indicating when the plunger has reached the shouldered portion of the sprue member I2 so as not to damage said member. This plunger may also have a tapered end 44 to facilitate entry into the sprue member 12, and may also have opposed notches to receive a tool for manipulating it.

By referring to Fig. 2, it will be noted that the opening in the lower flask section is sealed by reason of the flask section 26 engaging the countersunk seat in the base 34 and the opening in the upper flask section 2's is sealed by the plate 38 and flange M of the sprue member I2.

I claim:

1. In apparatus of the character described, a disc member having a central screw threaded opening, cavity and sprue forming members on said disc member consisting of a hollow metal cylindrical member having a restricted opening at one end, a cylindrical member inside of said hollow member and having a central passage, a tapered slitted neck portion projecting outwardly through said restricted opening and a screw threaded portion projecting outwardly through the other end of said hollow member, a pin de tachably mounted in said passage and projectin outwardly of said neck portion and a, wax pattern on the projecting end of said pin, the screw threaded portion of said inner cylindrical member being adapted to coact with the screw threaded opening of said disc member for moving said inner cylindrical member lengthwise of the hollow member and the diameter of said restricted opening being So proportioned relative to said tapered neck whereby said tapered slitted neck portion is contracted and pressed into gripping relation with said pin.

2. In apparatus of the character described, a disc member having a central screw threaded opening and a countersunk recess around said opening, a sectional hollow flask supported on said disc member above said opening for receiving investment material, an outer hollow cylindrical member on said disc member above said opening and extending inwardly of the flask, said outer hollow member having a screw threaded flange portion at its lower end seated in said countersunk recess, an inner cylindrical member extending through the opening in said disc member and into the interior of said outer hollow member, said inner cylindrical member having a central passage and a tapered neck portion normally projecting outwardly of the upper end of said outer member and into the flask, a pin detachably mounted in said central passage and projecting outwardly said neck portion into the interior of the flask and a wax pattern on the projecting end of said pin, said outer hollow member having opposed notches in the outer surface of its wall for receiving a tool for mounting the hollow member in the countersunk recess and for preventing motion of the outer hollow member relative to the investment material.

3. The combination with a frame having a base with a central countersunk recess in its upper surface, upstanding posts on said base, a sectional flask containing investment material seated in said recess, one section of said flask having a sprue member embedded in the investment material, said sprue member having a flange projecting above the investment material, and a plate detachably mounted on said posts for clamping said flask to the base, said plate having a central opening for receiving the flange carried by the sprue member with the flange fitted in the opening and formin a closure therefor.

4. In apparatus of the character described, a disc member having a central screw threaded opening and a countersunk recess around said opening, a sectional hollow flask supported on said disk member above said opening for receiving investment material, an outer hollow cylindrical member on said disc member above said opening and extending inwardly of the flask, said hollow member having a screw threaded flange portion at one end seated in said countersunk recess and the other end of the hollow member having a restricted opening within the flask, an inner cylindrical member extending through the opening in said disc member and into the interior of said outer hollow member, said inner cylindrical member having a central passage and a slitted tapered neck portion normally projecting outwardly through the restricted opening in said outer member into the flask and being so proportioned with respect to the restricted opening as to be compressed when moved outwardly through the opening, a pin detachably mounted in said central passage and projecting outwardly of the neck portion into the flask and a wax pattern on the projecting end of said pin, said inner cylindrical member having an externally screw 6 threaded end portion extending outwardly of the flask and coacting with the central screw threaded opening in said disc member for moving said inner cylindrical member lengthwise of the hollow member whereby said slitted tapered neck portion is pressed into gripping relation with the pin, said outer hollow member having opposed notches in the outer surface of its wall for receiving a tool for mounting the hollow member in the countersunk recess and for preventing motion of the outer hollow member relative to the investment material.

5. In apparatus of the character described, a disc member having a central screw threaded opening and a countersunk recess around said opening, a sectional hollow flask supported on said disc member above said opening for receiving investment material, an outer hollow cylindrical member on said disc member above said openin and extending inwardly of the flask, said hollow member having a screw threaded flange portion at one end seated in said countersunk recess and a restricted opening at the other end, an inner cylindrical member extending through the opening in said diSc member and into the interior of said outer hollow member, said inner cylindrical member having a central passage and a slitted tapered neck portion normally projecting outwardly through the restricted opening in said outer member and into the flask, a pin detach-v ably mounted in said central passage and projecting outwardly of the neck portion and a wax pattern on the projecting end of said pin, said inner cylindrical member having an externally screw threaded portion extending outwardly of the end of said outer member outside the flask and coacting with the central screwthreaded opening in said disc member for moving said inner cylindrical member and the diameter of said restricted opening being so proportioned relative to said tapered neck lengthwise of the hollow member whereby said slitted neck portion is pressed into gripping relation with the pin and thereby serving as a chuck member.

6. In apparatus of the character described, a disk member having a central screw threaded opening, cavity and sprue forming members on said disk member consisting of a hollow metal cylindricalmember secured at one end to said disk in the concentric relation to said threaded opening, a cylindrical member inside of said hollow member and having a central passage for the mounting of a pin, the upper end of the cylindrical member being tapered and longitudinally slitted, the restricted opening and tapered end being relatively proportioned whereby movement of the cylindrical member through the hollow member will compress said tapered slitted end for gripping the pin, and the lower end of the cylindrical member being threaded into the threaded opening of the disk for moving the cylindrical member through the hollow member.

IRVING HORDES.

REFERENCES CITED The following referenlces are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,541,869 Sprenger June 16, 1925 2,037,344 Schwartz Apr. 14, 1936 2,279,952 Pryor Apr. 14, 1942 

